Preparation of linear olefin products

ABSTRACT

A process for preparing and controlling the M n  of a reaction product comprising at least 90 mole % linear alpha olefins which includes polymerizing an ethylene containing gas in the presence of the reaction product of a Zirconium metal compound with R 2  AlX, wherein R is an alkyl group having about 1 to about 5 carbon atoms and X is Cl or Br, in the presence of a diluent at a temperature of about 75° to 200° C. and an ethylene pressure above about 50 psia, wherein the mole ratio of ethylene to olefin reaction product is above 0.8 throughout the reaction, wherein the product olefin concentration is greater than 5 wt. % based on the diluent and reaction product, wherein the M n  of said reaction product is controlled by the molar ratio of said R 2  AlX/ZrCl 4 , said molar ratio being less than about 1.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 179,655, f.Aug. 20, 1980, now Pat. No. 4,409,414, which in turn is a continuationof U.S. Ser. No. b 10,527, f. Feb. 9, 1979, now abandoned, which is adivision of U.S. Ser. No. 882,946, f. Mar. 2, 1978, now Pat. No.4,396,788, which is a continuation of U.S. Ser. No. 232,618, nowabandoned, f. Mar. 7, 1972, which is a continuation-in-part of U.S. Ser.No. 738,699, f. Dec. 13, 1968, now Pat. No. 3,662,021, which is acontinuation-in-part of U.S. Ser. No. 562,089, now abandoned, f. July 1,1966, which is a continuation-in-part of U.S. Ser. No. 428,836, f. Jan.28, 1965, now abandoned, and which is a continuation-in-part of U.S.Ser. No. 55,845, f. Sept. 8, 1960 which is now U.S. Pat. No. 3,168,588.

FIELD OF THE INVENTION

This invention relates to an improved process for preparing linearolefins, particularly linear alpha olefins. More particularly, thisinvention relates to an improved process for polymerizing ethylene toobtain linear olefins having a number average molecular weight rangingfrom about 70 to 700.

Still more particularly, this invention relates to an improved processfor polymerizing ethylene to obtain a product comprising at least 90mole % linear alpha olefins having a number average molecular weightgreater than about 200. Most particularly, this invention relates to animproved process for polymerizing ethylene to produce linear alphaolefins which comprises selectively terminating the polymerizationreaction and inhibiting deleterious side reactions.

PRIOR ART

It has been shown in the prior art (U.S. Pat. Nos. 2,993,942 and2,907,805) that hydrocarbon lubricating oils having a molecular weightin the range of 80 to 2000 could be prepared by polymerizing ethylenewith controlled catalyst compositions, diluents and under controlledtemperatures. The catalyst consisted of a transition metal halide and ahalogenated aluminum alkyl compound. It has also been found thatincreased oil yields, catalyst reactivity, and improved molecular weightcontrol could be obtained by the addition of a minor amount of a loweralkanol, as a catalyst modifier to the reaction system. Both themodified and unmodified systems described above resulted, under theconditions in the reaction, in the production of major portions ofolefins other than linear alpha olefin products, particularly ##STR1##olefins.

It has now been discovered that the polymerization of ethylene undercontrolled conditions to produce linear olefins can be made selectivefor linear alpha olefins by terminating the reaction by the addition ofan agent or agents to kill the activity of the catalyst and preventdeleterious side reactions. It has been found that the termination ofthe reaction by adding conventional catalyst killing agents, e.g.,alcohol or water results in a product other than one comprising at least90 mole % linear alpha olefins. The process of this invention requiredthe termination of the ethylene polymerization reaction by the additionof specific agents under specific conditions. The ethylenepolymerization reaction comprises a sequence of critical reactionvariables comprising, inter alia, a mole ratio of ethylene to product,use of a particular catalyst, a particular cocatalyst to catalyst moleratio, ethylene pressure, and product olefin concentration.

SUMMARY OF THE INVENTION

In accordance with this invention, therefore, an improved process forpreparing linear olefins, particularly linear alpha olefins, is providedwhich comprises polymerizing ethylene or an ethylene containing gas inthe presence of a catalyst comprising the reaction product of a Zrtransition metal halide, with an aluminum alkyl compound such that theultimate formula of the aluminum alkyl compound is AlR_(n) X_(3-n),wherein n is less than 2, R is a hydrocarbyl radical, and X is ahalogen, conducting the polymerization reaction in presence of asuitable diluent, at temperatures of about 75°-200° C. and ethylenepressures above about 50 psia, maintaining the mole ratio of ethylene toolefin reaction product above about 0.8 throughout the reaction, andkilling catalyst activity after at least about 5 wt.%, based on diluent,of product olefin has formed by adding an agent or agents to kill thepolymerization activity of the catalyst and preventing or inhibitingdeleterious side reactions. In an embodiment of this invention apolymerization killing agent is added and another agent, designed toprevent or inhibit side reactions, e.g., isomerization, is added eitherbefore, after or simultaneously with the polymerization killing agent.In another embodiment of this invention a single agent can be added tothe reaction mixture to accomplish both results, i.e., killpolymerization activity and inhibit deleterious side reactions. In yetanother, and preferred embodiment, the polymerization killing agent isadded to the reaction mixture prior to the removal of the ethylene fromthe reaction mixture. Generally, however, the agent or agents added tothe reaction mixture are added under relatively critical conditions.

The reaction can be terminated either by removing the ethylenecontaining gas thereby stopping the polymerization; or, by adding thepolymerization catalyst killing agent, thereby stopping thepolymerization activity of the catalyst.

While not wishing to be bound by any particular theory, it is believedthat the catalysts employed herein as ethylene polymerization catalyststend also to promote the copolymerization of the product olefins formedby the reaction. Now since the object of this invention is to produceand maintain a product comprising at least 90 mole % linear olefins, itis obvious that copolymerization of the reaction product will lead toincreased formation of branched products at the expense of linearproducts. Consequently, the reaction must be terminated at a suitablepoint where an economically feasible product yield has been obtained butprior to the occurrence of copolymerization to the extent that itreduces product purity to a level below about 90 mole % linear olefins.While generally conventional polymerization killing agents can be addedto the reaction mixture to terminate the polymerization activity of thecatalyst, e.g., water, alcohols, acids, etc., such agents tend toprotonate the catalyst and turn it into a strongly acidic Friedel-Craftscatalyst. A Friedel-Crafts catalyst in the reaction mixture, however,promotes isomerizations, alkylations, carbonium ion polymerizations,etc., which are deleterious in that such side reactions reduce thelinearity of the reaction product. Consequently, it is often-timesnecessary to add an additional agent, i.e., a base, to the reactionmixture to neutralize the Friedel-Crafts activity of the catalyst.

Generally, catalyst activity may be killed before or after the ethyleneis removed from the reaction mixture. When the catalytic activity iskilled after ethylene removal the polymerization killing agent must beadded within about one minute after ethylene removal. This is a criticalvariable in the preservation of the linear olefin reaction product.Thus, as previously mentioned, the polymerization catalyst also promotescopolymerization of the product olefin. However, copolymerization isinhibited due to the relatively high mole ratio of ethylene to produceolefin maintained throughout the reaction. (This ratio is maintained bythe high ethylene pressure, i.e., above about 50 psia ethylene, in thereaction mixture which promotes ethylene polymerization activity ratherthan copolymerization). When the ethylene has been removed theselectivity to ethylene polymerization is lost and copolymerization willbe promoted. In order to prevent copolymerization from destroying thelinear product it is critical that the polymerization activity of thecatalyst be killed within about one minute of ethylene removal. Afterkilling the polymerization activity with a conventional agent, theFriedel-Crafts activity must be neutralized, also within a criticalperiod. Thus, side reactions due to the presence of an acidic catalystcan also destroy the linear reaction product. The base, or neutralizingagent, must then be added within about on minute after thepolymerization activity is killed.

Of course, this invention contemplates the addition of the base prior tothe addition of the polymerization killing agent. Nevertheless,polymerization activity must be killed within about one minute ofethylene removal. Thus, if the base is added one minute after ethyleneremoval, the polymerization killing agent must be added simultaneously.However, the base may be added within about two minutes after ethyleneremoval if the polymerization killing agent is first added about oneminute after ethylene removal.

The foregoing critical relationships hold where the reaction isterminated at ambient temperatures, i.e., room temperatures of about18°-25° C., and above. It will be obvious to those skilled in the artthat if the temperature of the reaction mixture is reduced, i.e., takenbelow room temperature, after the polymerization activity is killed,addition of the base can be delayed somewhat. Of course, the lower thetemperature of the reaction mixture, the longer base addition can bedelayed. Using the very general rule that reaction rate doubles orhalves with each 10° C. change in temperature, a rough guide can beestablished and the period during which the base must be added (toprevent undue isomerizations, alkylations, etc.) can be readily found bysimple experimentation.

Thus, the general rule is that the polymerization activity of thecatalyst be killed within about one minute after termination of thereaction. It is preferred, however, to add the polymerization killingagent prior to the termination of the reaction, i.e., before theethylene is flashed off, a point which is obviously within the generalperiod just stated. This procedure eliminates observance of the criticalperiod when the reaction is terminated prior to killing polymerizationactivity. Additionally, the critical period for base addition is alsoobviated since the reaction mixture will be auto refrigerated due toflashing the ethylene, e.g., the temperature can be reduced to below-10° C. by auto refrigeration. Furthermore, at reduced temperatures thecatalyst can be washed out thereby eliminating the acid function andobviating the need for a neutralizing agent.

Some typical polymerization killing agents are water, alcohols, bothmono- and poly hydroxylic, cyclic and acyclic, aliphatic and aromatic;carboxylic acids, phenols, etc. The organic compounds which can be usedare those having from 1 to 15 carbon atoms, the lower carbon numberinexpensive compounds being preferred. Thus alcohols and acids havingfrom 1 to 8 carbons are preferred, with 1 to 4 carbons being mostpreferred. Examples of the most preferred killing agents include water,methanol, ethanol, isopropanol, t-butanol, and ethylene glycol.

Bases that can be employed to neutralize Friedel-Crafts activity can beany base that will effectively neutralize this acid function. Generally,such bases can be broadly characterized as Lewis bases. Such materialswhich can be used in the practice of this invention include causticssuch as alkali metal and alkaline earth metal hydroxides and carbonates,ammonium hydroxide and quaternary ammonium bases and organic bases suchas organic nitrogen compounds, e.g., ammonia, amines and cyclic nitrogenbases, and ethers, etc. As specific example, there can be named lithiumhydroxide, sodium hydroxide, potassium carbonate, magnesium hydroxide,calcium carbonate, tetramethylammonium hydroxide, C₁ -C₁₀ aliphaticamines, e.g., ethylamine, methyl-amine and aniline-p-toluidine, ammonia,heterocyclic nitrogen compounds, e.g., pyridine, and tetrahydrofuran.These bases may be used alone, in mixtures or dissolved in solvents suchas water, alcohols, glycols, etc. The preferred bases are sodiumhydroxide or ammonia dissolved in water or alcohols. Although largeramounts may be used, it is desirable to use 0.5 to 2 moles of base peratom of halogen in the catalyst, preferably about stoichiometricamounts. It is obvious that a base such as sodium hydroxide dissolved inwater or alcohols serves to kill polymerization activity simultaneouslywith neutralization. Lewis bases kill polymerization activity bycomplexing more strongly than alpha olefins with the transition metalsite. On the other hand, protonic agents kill polymerization activity bydestroying the metal-carbon bonds of the catalyst. Thus, a base isneeded in addition to the protonic agents to neutralize theFriedel-Crafts activity of the catalyst residues, whereas a Lewis basesuch as triethylamine inactivates both types of catalyst activity.

The catalyst which can be used is a complex reaction product which isobtained by partially reacting a reducible transition metal halide ofGroup IVB to VIB or VIII with an aluminum alkyl compound such that theultimate formula of the aluminum alkyl compound is AlR_(n) X_(3-n),wherein n is less than 2, R is alkyl, cycloalkyl or aralkyl, preferablycontaining 1 to 20 carbon atoms, for example, methyl, ethyl, isobutyl,cyclohexyl, benzyl, etc., and X is Cl or Br or I. While most transitionmetal halides are suitable components of the catalyst complex, when thedesired product is the branched chain olefins of the prior art, it hasbeen found that compounds such as VCl₄ and FeCl₃ are unsuitable for thepreparation of linear alpha olefins. The preferred transition metalcatalyst components is a Zr metal compound having a valency of 4, andmay be represented by the formula: ZrX_(a) A_(b), wherein a=3 or 4, b-0or 1 and a+b=3 or 4, X═Cl or Br and A is Cl or Br or an anion derivedfrom a protonic compound such as an alcohol (R'OH) or a carboxylic acid(R'COOH). The R' of the protonic compound may be an alkyl, aryl, aralkylor cycloalkyl group. The ZrX_(a) A_(b) component may be made in situ byreacting ZrX₄ with the protonic compound. Thus, the preferred transitionmetal component of this invention may be selected from the group ZrX₄,ZrX₃ OR' and ZrX₃ OOCR'. Typical examples of such compounds are ZrCl₄,ZrBr₄, ZrX₃ OC₂ H₅, and ZrX₃ OOCCH₃.

The transition metal component may also be a halide, an alkoxide or acarboxylate derivative of tetravalent zirconium or hafnium having thegeneral formulas MX_(n) (OR)_(4-n) and MX_(n) (OOCR')_(4-n), where M═Zror Hf, X-Cl or Br, n=0 to 4 and R' may be an alkyl, aryl, aralkyl orcycloalkyl group. When these components are reacted with the excessaluminum alkyl chlorides, exchange or ligands takes place involvinghalide, alkyl, alkoxide and carboxylate groups. In addition to exchangeof aluminum alkyl groups with transition metal ligands, the aluminumhalide groups can also exchange with alkoxy and carboxyl groups on thetransition metal compound. These compounds may also be made in situ byreacting the more readily available MX₄ with R'OH or R'COOH. Thealcohols may be unsaturated as in the case where they are the enol formsof carbonyl compounds such as acetyl acetone. Typical examples includeZrCl₄, ZrBr₄, ZrCl(OEt)₃, ZrCl₂ (OC₁₀ H₂₁)₂, ZrBr₃ oBu, Zr(OPr)₄,Zr(OBu)₄, ZrCl₂ (Oφ)₂, ZrCl₂ (OOCC₉ H₁₉)₂, ZrCl(OOCφ)₃, ZrCl₃ OOCCH₃,ZrCl₂ glycoxide, Zr acetyl acetonate, ZrCl₃ (O-cyclohexyl), HfCl₄,HfBr₄, Hf(OBu)₄, etc., in which the hydroxy groups are not attached toadjacent carbon atoms are also useful. Especially preferred anddesirable are: tertiary butanol, secondary butanol, iso- or n-butanol,and isopropanol. These alkanols are utilized in a minor amount, i.e. sothat the ratio of ROH/R (based on aluminum alkyl) after alkylation orreduction of the transition metal is not greater than 0.5.

It has been surprisingly found that when one employs a catalyst systemcomprising an R₂ AlX wherein R is an alkyl group having about 1 to 5carbons, preferably ethyl, and X is Cl or Br, preferably Cl; and ZrCl₄for the polymerization of ethylene, the M_(n) of the formed polyethyleneincreases as the molar ratio of R₂ AlX/ZrCl₄ decreases, wherein themolar ratio of Al/Zr is less than about 1, more preferably less thanabout 0.5.

Ethylene is unique in the instant invention in that other olefins do notrespond to give linear alpha olefins. Therefore, it is desirable to useessentially pure ethylene or mixtures of ethylene with inert gases asthe feed for the process of this invention. Ethylene feeds containingminor amounts of other olefins may be used provided that the extent ofcopolymerization does not decrease product linearity below 90%.

Polymerization diluent is not a critical feature of this invention. Theuseable diluents are aromatic hydrocarbon and haloaromatic solvents aswell as aliphatics and naphtenics. Less preferred solvents arehalogenated aliphatic compounds which, while capable of being employedin the process of preparing linear alpha olefins, require theutilization of higher pressures to achieve average molecular weights ofthe same order as the preferred solvents. The preferred diluents includehalogenated aromatics such as chlorobenzene, dichlorobenzene,chlorotoluene, etc., aromatics such as benzene, toluene, xylenetetrahydronaphthalene, etc., aliphatics such as pentane, heptane,iso-octane, etc., a naphthenes such as cyclohexane, methylcyclohexane,decahydronaphthalene, etc. The suitable halogenated aliphatic diluentsinclude methyl chloride, ethyl chloride, dichloromethane, etc. Mixturesof these diluents may be used. Also, mixtures of the above types withaliphatic or naphthenic solvents may be used. The diluent or diluentmixture may be used to control the product molecular weight distributionto obtain maximum selectivity to the desired olefin products.

The prior art obtained highly branched olefins (60%) when using theclosely related catalyst and diluent systems at pressures of 7 to 30psig., e.g., British Pat. No. 974,577. Ethylene pressures above 50 psiaare essential for making linear olefins in high selectivities. Althoughsome variations are permitted depending upon the catalyst composition,diluent and temperature, the preferred pressures are above about 80 to100 psia in order to produce commercially attractive yields (at leastabove 5 weight % and preferably above 10 weight % olefins in the reactoreffluent) of linear alpha olefins having a purity greater than about 90mole %. The most preferred range is above 100 psia ethylene pressure. Atvery high ethylene pressures the process may become uneconomical becauseof the equipment requirements and ethylene recycle. Nevertheless, higherpressures tend to increase the selectivity of the reaction to linearalpha olefins.

The ratio of moles of ethylene to the moles of products throughout thereaction and insured by the ethylene pressures referred to above, mustbe above about 0.8 in order to effect the selective synthesis of linearolefins from ethylene and inhibit copolymerization effects. Thepreferred ratio of ethylene to products is above about 2.0. The upperlimit of the mole ratio of ethylene to product is not critical. The moleratio of ethylene to product must be above 0.8 to the product formedcontains more than 10% branched chain olefins at product concentrationsrequired to obtain commercially attractive yields.

The catalyst of this invention enables the process for making linearalpha olefins to be carried out at temperatures of about 75° to about200° C., preferably between about 100° C. and about 180° C. Theselection of a particular temperature will permit control of the numberaverage molecular weight of the wax product. With zirconium and hafniumcatalysts, temperatures as high as about 200° C. can be used withoutmaking excessive amounts of polyethylene. However, the high temperaturescause product isomerization and require higher ethylene pressures toprevent copolymerization which make them less attractive. The preferredtemperatures to obtain high purity linear alpha olefins with zirconiumtetrachloride catalysts are between about 75 to about 200° C. and, morepreferably, between about 100 to about 180° C. and most preferably about120° to 150° C., to obtain total product M_(n) >200.

Reaction times are not particularly critical when operating under thepreferred conditions and they will normally be in the range of 0.1 to 5hours to obtain product concentrations greater than 5% by weight in thediluent. The process may be carried out in batch or continuousoperation. However, high product purity and high concentration areachieved most easily in batch reactions or in continuous systemsoperating under essentially plug flow conditions. A reactor may consistof a long pipe through which the diluent and catalyst flow with ethylenebeing introduced at many points along the pipe to maintain the desiredethylene concentration. In such a system monomer concentration need notbe constant but may be controlled differently in different sections ofthe reactor to achieve the best balance of activity, molecular weightand product purity. Stirred tank reactors may be operated in series toapproach plug flow.

After the catalyst has been effectively neutralized, the residues may beremoved from the products in any conventional way, such as washing withwater or aqueous caustic, adsorption, ion exchange resins, etc. If thecatalyst has been neutralized according to this invention, the productsmay be distilled directly from the catalyst residues without decreasingproduct purity. However, it is preferred to remove the residues beforedistillation in order to minimize deposits in the distillation towers.

Based on the teachings of this invention to destroy both polymerizationand Friedel-Crafts activity to permit isolation of greater than 95% purelinear alpha olefins, it is clearly within the scope of the invention toaccomplish the same results by alternatives such as rapid solventextraction or solid adsorption techniques, particularly if these areused before all of the ethylene has been flashed. However, suchtechniques are generally less effective than the preferredneutralization procedure.

The following examples are submitted in order to more particularly pointout applicant's invention but are not to be constructed as limitationsupon the scope of the instant invention as described in the appendedclaims.

EXAMPLE 1

A series of runs were made to determine the effect of ethylene pressureon product linearity. All were carried out at -20° C. using 500 ml ofeither chlorobenzene or xylene diluent. The proportions of catalystcomponents were maintained constant, although total catalystconcentration was varied by a factor of four. The TiCl₄ in 400 mldiluent was added to the reactor under dry nitrogen and cooled at -20°C. The t-butyl alcohol and AlEt₂ Cl were mixed 5 minutes in 100 mldiluent before adding the AlEtCl₂. The latter was added to the reactorand the total mixture allowed to react 15 minutes at -20° C. High purityethylene was obtained by passing commercial C.P. ethylene over copperoxide at 205° C. to remove oxygen and then through 3A molecular sievesto remove water. It was stored in a one-gallon reservoir at 1000 psig.After the catalyst pretreatment, the reactor contents were subjected tohigh speed stirring. Ethylene was added as necessary to maintainpressure and the temperature was kept at -20° C. by circulating coolantthrough coils around the reactor.

The results are summarized in Table I. After killing the catalyst withabout 25 to 50 ml methanol containing NaOH, the product was water-washedtwice and dried over K₂ CO₃. The products were analyzed quantitativelyfor olefin types by infrared, and the split between linear and branchedproducts was determined by quantitative gas chromatography on a sampleof total reactor product. Using a four-foot column of silicone gumrubber and temperature programming, it was possible to obtain the yieldof each product up to C₃₆ H₇₂. Product linearity is expressed as mole %in the C₁₂₋₂₀ fraction. It was compared on the C₁₂₋₂₀ cuts because thiswas the most accurate analysis considering volatility losses from C₄₋₁₀and G.C. resolution of the branched and linear olefins about C₂₀. Thelinearity of the total product is much higher than that shown for theC₁₂₋₂₀ fraction because in all pressure runs the C₄₋₁₀ fraction isessentially 100% linear, and it is a major portion of the total product.

As shown in Table I, the selectivity to linear alpha olefins increasessharply above about 50 psia and becomes greater than 90% above about 100psia. At still higher ethylene pressures, selectivity rapidly approaches100% in the C₁₂₋₂₀ fraction. Excellent results were obtained with eitherchlorobenzene or xylene diluent. In addition to the effect on olefinlinearity, ethylene pressure may be used together with catalyst,composition, solvent polarity and polymerization temperature to controlthe product molecular weight. As shown in Table I for chlorobenzenediluent, the number average molecular weight increased from 98.8 atatmospheric pressure to 147 at 500 psia.

                                      TABLE I                                     __________________________________________________________________________                                     % Linear                                         mmoles (a)     psia                                                                              g. Product/                                                                          (c)                                                                              Olefins in                                   Run A/B/C/D                                                                             Diluent                                                                            Hours                                                                             C.sub.2 H.sub.4                                                                   g/TiCl.sub.4 /Hr.                                                                     --M.sub.n                                                                       C.sub.12-20                                  __________________________________________________________________________    3   12/12/2/2                                                                           C.sub.6 H.sub.5 Cl                                                                 1    15 (b)                                                                           45      98.8                                                                            67                                           4   12/12/2/2                                                                           C.sub.6 H.sub.5 Cl                                                                 1    55 95     100.5                                                                            70                                           5   12/12/2/2                                                                           Xylene                                                                             1   140 105    121.4                                                                            98                                           6   6/6/1/1                                                                             C.sub.6 H.sub.5 Cl                                                                 1   165 147    112.6                                                                            97                                           7   3/3/0.5/0.5                                                                         C.sub.6 H.sub.5 Cl                                                                 2   250 74     121.3                                                                            99                                           8   12/12/2/2                                                                           Xylene                                                                             1   250 97     140.0                                                                            100                                          9   12/12/2/2                                                                           C.sub.6 H.sub.5 Cl                                                                 0.5 500 126    147.0                                                                            100                                          __________________________________________________________________________     ##STR2##                                                                      (b) Gaseous ethylene bubbled continuously through diluent at atmospheric      pressure.                                                                     (c) Number average molecular weight of total olefin product.             

EXAMPLE 2

A catalyst solution containing 1.5 mmoles AlEt₂ Cl, 3.0 mmoles AlEtCl₂and 3.0 mmoles TiCl₄ in 250 ml xylene was pretreated 30 minutes at 15°C., cooled to 0° C. and ethylene added rapidly. Polymerization wascarried out two hours at 0° C. and 520 psia ethylene pressure. Samplesof the total reactor product were taken hourly and analyzed as inExample 1.

In taking the reactor samples, the ethylene is allowed to flash off atatmospheric pressure, thereby refrigerating the sample. The first hoursample (10 ml) was allowed to stand 15 minutes before killing thecatalyst with 1 ml of 1 M NaOH in methanol. The second hour sample (18ml) was pressured from the reactor directly into a vessel containing the1 ml of 1 M NaOH in order to kill the catalyst immediately. The amountof NaOH was taken to be approximately equivalent to the chloride contentof the catalyst in the sample.

Alkylation took place so extensively in the first hour sample that itwas impossible to do the usual analysis. Product concentration wasestimated to be about 30 to about 40 weight %. No linear alpha olefinswere indicated by infrared analysis. The product was prediminantlyalkylated xylene.

The second hour sample was 96.9% linear alpha olefins despite the factthat product concentration was much higher (53.6 weight %). By analogywith all other experiments, the first hour sample should have had thehighest linearity; in this case, an estimated 98 to 99% if the catalysthad been destroyed immediately after flashing ethylene.

This example illustrates that high purity olefins can only be obtainedby rapid destruction of the catalyst activity after flashing ethylene.

EXAMPLE 3

A catalyst solution was prepared by reacting 12 mmoles AlEt₂ Cl and 2mmoles t-butanol in 95 ml chlorobenzene for 5 minutes, then adding 12mmoles AlEtCl₂. 400 ml chlorobenzene containing 2 mmoles TiCl₄ wascharged to the reactor, cooled to -20° C., the aluminum alkyl solutionwas added, and the catalyst was pretreated 15 minutes at -20° C.Ethylene was charged to 155 psia and polymerization was continued onehour at 150 to 160 psia and -20° C.

The total reactor product was flashed into 100 ml methanol without anybase present. After filtering off 4.8 grams wax, the filtrate waswater-washed, dried over K₂ CO₃ and distrilled using a 15 plateOldershaw column at 20/1 reflux ratio. Infrared analysis of the C₄ -C₈cut gave only 80% linear alpha olefins and 20% internal olefins (TypeII-trans). Since some Type II-cis olefins would have been producedsimultaneously by isomerization, the linear alpha olefin purity wasconsiderably less than 80%.

Experiments in which the products were flashed into methanol plus NaOHgave over 98% pure linear alpha olefins. In the infrared analyses ofthese samples, the Type II-trans absorption at 10.3 was barelydiscernible.

This example illustrates that rapid quenching of the catalystpolymerization activity is not sufficient to obtain high purity alphaolefins. In the absence of a base, double bond isomerization occurs toproduce the less desirable internal olefins. It shows that it iscritical to destroy the Friedel-Crafts activity of the catalyst as wellas the polymerization activity. Besides double bond isomerization,residual catalyst Friedel-Crafts activity could also cause alkylationand cationic polymerizations which would further decrease the alphaolefin purity.

With high polymers any residual polymerization or Friedel-Craftsactivity has a negligible effect, if any, on product properties. In aprocess for making linear alpha olefins, however, it is critical todestroy or neutralize both types of catalyst activity.

EXAMPLE 4

Following the procedure of Example 3 but terminating the polymerizationwith 10 ml methanol plus 10 ml 6H NH₄ OH prevented isomerization andpreserved the alpha olefin purity.

EXAMPLE 5

A series of runs were made to determine the effect of quenching variouscatalyst compositions. The reaction conditions are set forth in TableII. In each run the reaction was quenched with a mixture of methanol andNaOH. It is to be seen from Table II that the instant process resultedin a highly linear product.

                  TABLE II                                                        ______________________________________                                        Run          1        2        3      4                                       ______________________________________                                        AlEtCl.sub.2, mmoles                                                                       5        2        5      0.5                                     AlCl.sub.3, mmoles                                                                         0        0        0.2    0                                       TiCl.sub.4, mmoles                                                                         1        1        0.05   1                                       Solvent      Xylene   Xylene   C.sub.6 H.sub.5 Cl                                                                   C.sub.6 H.sub.5 Cl                      ml           125      125      250    250                                     Pretreat, °C./min.                                                                  25/60    50/30    50/30  50/30                                   Al/Ti Mole Ratio                                                                           5        2        104    0.5                                     Et/Al Ratio (a)                                                                            0.8      0.5      0.95   0                                       Polymerization                                                                Temp. °C.                                                                           15       50       50     50                                      C.sub.2 H.sub.4, psia                                                                      400      400      400    400                                     Time, Hrs.   1        1        3      0.5                                     Results                                                                       Yield, g (b) 132      92       23     51                                      Linearity, Mole % (c)                                                                      91.5     91.2     95.2   94.3                                     --Mn        113      128      114    116                                     ______________________________________                                         (a) Assuming monalkylation of TiCl                                            (b) Excluding 10-20% losses during workup                                     (c) Determined on C.sub.12-20 fraction                                   

EXAMPLE 6

A catalyst solution was prepared by mixing 0.1 mmole ZrCl₄ and 0.2 mmolephenol in 40 ml chlorobenzene for 5 minutes at 50° C., then adding 0.4mmole Al₂ Et₃ Cl₃ and pretreating 15 minutes at 60° C. The solution wasrinsed into a pressure catalyst bomb with an additional 10 mlchlorobenzene and pressured with ethylene into the reactor containing150 ml chlorobenzene and 890 psia C₂ H₄ at 70° C. The temperature andpressure were immediately raised to 75° C. and 1015 psia ethylenepressure and maintained for 30 minutes.

G.C. samples were flashed into 1 M NaOH in methanol, n-heptane was addedand the solutions were washed with aqueous K₂ CO₃ solution, separatedand dried over solid K₂ CO₃. Analyses were carried out using a 15 ft.column of SE-30 (2% on Choromsorb G) and temperature programming to 340°C. The yield of olefins between C₄ and about C₄₀ after 15 minutes was 48g and after 30 minutes it was 90 g. Linear alpha olefin purity in theC₁₂₋₂₀ fraction was 99+%. Extraction of the wax with boiling n-heptaneless than 0.1 g insoluble product.

EXAMPLE 7

The procedure of Example 6 was followed except that n-butanol was usedin place of phenol and it was mixed with either the ZrCl₄ or the ethylaluminum sesquichloride for 5 minutes at 25° C. before adding the secondcatalyst component and pretreating. In Runs 1 and 2 of Table III, noalcohol was added. Variations in catalyst composition, catalystpretreatment and reaction conditions are given in the Table.

                                      TABLE III                                   __________________________________________________________________________                          Oligomerization                                                          Catalyst                % Linear                                mmoles        Pretreat,                                                                          Temp.                                                                             Time,                                                                             g. Olefins/                                                                              Olefins in                           Run                                                                              A/B/C/D (a)                                                                            Diluent                                                                            OC/min.                                                                            °C.                                                                        Min.                                                                              g. Catalyst (b)                                                                       --M.sub.n                                                                        C.sub.12 -C.sub.20                   __________________________________________________________________________    1  0.4/0.4/0.1/0                                                                          C.sub.6 H.sub.5 Cl                                                                 60/30                                                                              75  30   473     93                                                                               99+                                 2  0.2/0.2/0.05/0                                                                         C.sub.6 H.sub.5 Cl                                                                 80/30                                                                              100 30                                                                            1295                                                                              111     98                                      3  0.4/0.4/0.1/0.4                                                                        C.sub.6 H.sub.5 Cl                                                                 50/15                                                                              75  60  1090    148                                                                              98                                   4  0.4/0.4/0.1/0.4 (c)                                                                    C.sub.6 H.sub.5 Cl                                                                 90/15                                                                              75  30   385    158                                                                               99+                                 5  0.2/0.2/0.05/0.2                                                                       C.sub.6 H.sub.5 Cl                                                                 50/15                                                                              125 30  1275    154                                                                              95                                   6  0.4/0.4/0.1/0.4                                                                        n-C.sub.7 H.sub.16                                                                 50/15                                                                              75  30   262    140                                                                               99+                                 __________________________________________________________________________     (a) Catalyst AlEt.sub.2 Cl/AlEtCl.sub.2 /ZrCl.sub.4 /nBuOH.                   (b) Excluding the nbutanol.                                                   (c) The nbutanol was reacted first with the Al.sub.2 Et.sub.3 Cl.sub.3        rather than with ZrCl.sub.4.                                             

In all runs catalyst activity was excellent. The purity of the linearalpha olefins in the C₁₂₋₂₀ fraction ranged from 95% to nearly 100%.Total product molecular weight ranged from 93 to 158, illustrating thecontrol of product distribution. At M_(n) =93, selectivity to C₄₋₁₀ is76.8% whereas at the higher molecular weights (M_(n) =140-158), oneobtains the highest selectivity to C₁₂₋₁₈ detergent range olefins.

No significant amount of polyethylene was obtained in any of theseexperiments.

EXAMPLE 8

The procedure of Example 7 was followed except that zirconium propoxideand zirconium dipropoxy dichloride were performed rather than being madein situ by reacting ZrCl₄ with propanol. Variations in catalystcomposition, pretreatment and reaction conditions are summarized inTable IV.

                                      TABLE IV                                    __________________________________________________________________________                   Catalyst                % Linear                                  mmoles      Pretreat,                                                                          Temp. Time,                                                                             g. Olefins/                                                                            Olefins in                             Run                                                                              A/B/C (a)                                                                           Diluent                                                                             °C./min.                                                                    °C.                                                                          Min.                                                                              g. Catalyst                                                                          --M.sub.n                                                                       C.sub.12 -C.sub.20                     __________________________________________________________________________    1  0.2/0/0.2                                                                           n-C.sub.7 H.sub.16                                                                  50/15                                                                              50    30  0     -- --                                     2  0.2/0.6/0.2                                                                         N--C.sub.7 H.sub.16                                                                 80/5 50    30  572   188                                                                               99+                                   3  0.9/0.9/2                                                                           C.sub.6 H.sub.5 Cl                                                                  50/15                                                                              75-170 (c)                                                                          15  652   141                                                                              95                                     4  0/0.8/                                                                              C.sub.6 H.sub.5 Cl                                                                  60/15                                                                              50    30  417   172                                                                               99+                                      0.2 (b)                                                                    __________________________________________________________________________     (a) A/B/C = AlEt.sub.2 Cl/AlEtCl.sub.2 /Zr(OPr).sub.4                         (b) ZrCl.sub.2 (OPr).sub.2 was used in place of the tetraalkoxide.            (c) Lost temperature control allowed temperature to rise to about             170° C. momentarily. Most of the run was at 80° C.         

Run 1 used equimolar amounts of AlEt₂ Cl and Zr(OPr)₄ and was completelyinactive, whereas Run 2 used 8:1 Al:Zr mole ratio and was very active.This illustrates that preformed zirconium alkoxides require an excess ofaluminum alkyl halide just as was found for the in situ preparationusing the alcohols. In either case, the ratio of ROH (or RO groups onthe Group IVB metal)/R (based on aluminum alkyl) after alkylation of thetransition metal is preferably less than about 0.5.

Run 3 produced a small amount of polyethylene, presumably because of theexcessively high reaction temperature reached momentarily. Based on thisresult and those in Example 7, the maximum desirable reactiontemperature is about 150° C. for the zirconium catalysts. Product puritydrops at the higher temperatures due to copolymerization andisomerization of the alpha olefins so that the preferred reactiontemperature for making high purity linear alpha olefins is below 125°C., most preferably below about 75° C.

Run 4 shows that preformed zirconium alkoxy chlorides are as effectiveas those formed in situ form the alcohols. Having demonstrated theutility of ZrX₄, ZrX₂ (OR)₂ and Zr(OR)₄, it is clear that other mixedalkoxy halides will also be useful (for example, ZrCl₃ OR, ZrCl(OR)₃,etc.).

EXAMPLE 9

The procedure of Example 6 was followed except that 0.2 mmoleneodecanoic acid (Enjay Chemical Co.) was used in place of phenol.Neodecanoic acid is a mixture of C₁₀ acids having three alkylsubstituents on the alpha carbon (R₁ R₂ R₃ CCOOH). The mole ratio of 2acids per ZrCl₄ yields the dichlorodicarboxylate, ZrCl₂ (OOCR)₂.

After 30 minutes at 75° C. and 1015 psia ethylene pressure, the olefinyield was 68 g and the purity was 99+%.

EXAMPLE 10

The procedure of Example 6 was followed except that 0.4 mmoleacetylacetone was used in place of phenol and the ZrCl₄ -acetylacetonereaction product was pretreated 15 minutes at 50° C. with 0.8 mmole Al₂Et₃ Cl₃. The alcohol form (enol) of acetylacetone reacts with thecatalyst in the same manner as saturated alcohols. The product (91 g)was 99% pure linear alpha olefins.

EXAMPLE 11

The procedure of Example 6 was followed except that 0.2 mmole benzoicacid was used in place of phenol, yielding a clear, colorless solutionwith the 0.1 mmole ZrCl₄. Addition of 0.6 mmole Al₂ Et₃ Cl₃ andpretreatment for 15 minutes at 50° C. produced a clear, very lightyellow solution. After 30 minutes oligomerization at 75° C. and 1015psia ethylene pressure, a high yield of high purity linear alphs olefinswas obtained.

EXAMPLE 12

A slurry of ZrCl₄, DEAC, 5 g n-C₁₁ H₂₄ internal standard and 500 mln-heptane was charged at about 50° C. to the reactor under nitrogen, thereactor gas phase was evacuated briefly, the reactor temperature wasincreased to 20° C. below the final run temperature, ethylene waspressured rapidly to reach 7 MPa to run temperature in less than about 2minutes. Ethylene was fed continuously to maintain 7 MPa.

The effect of DEAC/ZrCl₄ ratio on product M_(n) was studied at two runtemperatures (120° C. and 130° C.).

                                      TABLE V                                     __________________________________________________________________________       DEAC                                                                              ZrCl.sub.4                                                                            Temp.                                                                             Time,                                                                             Rate      %                                            Run                                                                              mmol                                                                              mmol                                                                              Al/Zr                                                                             °C.                                                                        Min.                                                                              g/g ZrCl.sub.4 /hr                                                                    --M.sub.n                                                                       Purity                                       __________________________________________________________________________    A  0.40                                                                              0.10                                                                              4.0 120 15  32,000 150                                                                              95.5                                         B  0.10                                                                              0.10                                                                              1.0 120 15  18,000 196                                                                              98.5                                         C  0.10                                                                              0.20                                                                              0.5 120 15  17,000 215                                                                              96.3                                         D  0.04                                                                              0.16                                                                               0.25                                                                             120 15  11,600 248                                                                              99.6                                         E  0.08                                                                              0.08                                                                              1.0 130 15  12,600 174                                                                              99.3                                         F  0.06                                                                              0.24                                                                               0.25                                                                             130 15   6,100 224                                                                              99.9                                         __________________________________________________________________________

Surprisingly, M_(n) increased with decreasing Al/Zr ratio, especiallybelow 1/1. This is particularly attractive for making olefin wax becausethe selectivity to wax increases rapidly at total product molecularweights above 200.

The effect of Al/Zr ratio is directly opposite to that taught by Zieglerfor DEAC/TiCl₄ ratio in which polyethylene molecular weight increasessharply with increasing ratio. (Belgium 540,459 (Feb. 9, 1956); see Raffand Doak, Crystalline Olefin Polymers I, Interscience 1965, p. 372) FIG.1 contrasts the Ziegler data with our DEAC/ZrCl₄ results. Clearly, weare dealing with different catalyst species (tetravalent Zr) rather thanthe reduced transition metal species in typical Ziegler catalysts. Thusone cannot extrapolate the broad disclosures of reduced Ziegler-typecatalysts for polyethylene to the alkylated but unreduced tetravalentcatalysts for ethylene oligomerization to alpha olefins.

What is claimed is:
 1. A process for preparing and controlling the M_(n)of a reaction product comprising at least 90 mole % linear alpha olefinswhich comprises polymerizing an ethylene containing gas in the presenceof the reaction product of ZrCl₄ with R₂ AlX, wherein R is an alkylgroup having about 1 to about 5 carbon atoms and X is Cl or Br, in thepresence of a diluent at a temperature of about 75° to 200° C. and anethylene pressure above about 50 psia, wherein the mole ratio ofethylene to olefin reaction product is above 0.8 throughout the reactionwherein the product olefin concentration is greater than 5 wt.% based onthe diluent and reaction product, wherein the M_(n) of said reactionproduct is controlled by the molar ratio of said R₂ AlX/ZrCl₄, saidmolar ratio being less than about
 1. 2. A process according to claim 1,wherein said molar ratio is less than 0.5.
 3. A process according toclaim 1, wherein said R₂ AlX is R₂ AlCl.
 4. A process according to claim1 wherein said temperature is about 100° to about 180° C.
 5. A processaccording to claim 1 wherein said temperature is about 120° to about150° C.
 6. A process according to claim 2 or 3 wherein said ethylenepressure is at least 1000 psig.